1. Field of the Invention
The present invention relates to an optical disk and an optical disk device which is preferably used in a stationary electronic apparatus such as a personal computer, a portable electronic apparatus such as a notebook computer, a personal digital assistant, or a portable display unit, or a recorder for recording images. More particularly, the invention relates to an optical disk having a label surface on which visually perceivable characters and images can be recorded.
2. Description of the Related Art
Optical disk devices have widely spread as data reproduction devices in the fields of computers and audio visual apparatus because of the large recording capacity of optical disks and the ease of handling of optical disks. The recent spread of optical disk reproducing apparatus has provided an infrastructural background for remarkable spread of recordable optical disks in which various data such as images and music can be recorded, e.g., CD-R/RW, DVD-RAM, DVD-R/RW, and DVD+R/RW and recordable optical disk devices. In such recordable optical disk devices, a recording surface formed in a plane of an optical disk is irradiated with laser light to record images and music thereon.
In the situation where recordable optical disks and apparatus are rapidly increasing as described above, several proposals have been made, in the form of products, on how to provide visually perceivable characters and images on an optical disk to show contents recorded on a data recording surface of the optical disk. One approach is to use a printer in the related art. A label surface may be provided opposite to a data recording surface of an optical disk to allow direct printing on the label with an inkjet printhead. Alternatively, a sheet-like label may be printed and may thereafter be cut in the shape of an optical disk to apply the label to a label surface of the disk (see FIG. 1).
Another approach is to record a visible image on an optical disk using a laser loaded on an optical disk device. This approach includes a proposal in which a difference in reflectivity between a recorded part and an unrecorded part of a data recording layer of an optical disk is used (see FIG. 2) and a proposal in which a photosensitive layer, a thermosensitive layer, or a sheet having photosensitive/thermosensitive properties is applied to a label surface of an optical disk according to the related art to record a visible image on the same with a laser.
Examples of the above-described prior art are shown in JP-A-2003-16650 and JP-A-2003-203348 and JP-A-2002-25222.
In the above-described configurations according to the related, the first recording layer for recording substantial information and the second recording layer for forming a visible image are provided very close to each other. As a result, when a high power laser is used for purposes such as increasing recording density or recording speed by the use of a short wavelength laser such as a red laser or blue laser, the first and second layers may be adversely affected. Specifically, when a visible image is formed on the second recording layer using emission at high power from a short wavelength laser, information on the first recording layer may be destroyed.